What is the diaphragm?
The diaphragm is a large, dome-shaped, sheet of muscle that separates the thoracic cavity from the abdominal cavity. The central region of the diaphragm does not move, and provides support to the overlying heart in the central mediastinum region of the thoracic cavity. On either side of the mediastinum, lie the two lungs, which also sit above the diaphragm. The movement of the diaphragm below the lungs make the breathing process possible.
Contraction of the diaphragm muscle induces expansion of the lungs by creating negative pressure around them. The expansion of the lungs draws air into the lungs, resulting in the inspiration phase of the breathing cycle. Relaxation of the diaphragm muscle reduces the negative pressure around the lungs, resulting in an elastic recoil of the lungs back to their original dimensions. This pushes the air out of the lungs, resulting in the expiration phase of the breathing cycle.
The contractions and relaxations of the diaphragm are controlled by nerve signals emanating from the respiratory centers located in the brain. These signals are carried to the diaphragm by the phrenic nerve.
How does the diaphragm become paralyzed?
Since diaphragm plays a critical role in the breathing process, a paralysis of this muscular sheet can affect (and even stop) the breathing process. Breathing may not stop entirely and immediately with a diaphragm paralysis. Other accessory breathing muscles that assist in the breathing process can still enable a person to breathe. However, the breathing in these cases will be highly labored since the accessory muscles are not as strong as the diaphragm.
Even though the diaphragm is a single muscular sheet, paralysis of the diaphragm may affect only a part of the whole muscle. Diaphragm paralysis can be classified into unilateral (one-sided) paralysis or bilateral (two-sided) paralysis. Unilateral paralysis only affects about 20% of the breathing capacity, and is, therefore, largely asymptomatic.
The signs and symptoms are quick to arise if the paralysis of the diaphragm is bilateral, resulting in severe respiratory distress. Presence of accompanying diseases of the airways and the lungs worsen the condition further. Severe paralysis of the diaphragm may eventually cause total respiratory failure and death.
Signs and Symptoms
The signs and symptoms of diaphragm paralysis depend on the extent of the paralysis. The clinical signs and symptoms of diaphragm paralysis can be classified into two groups, based on whether the paralysis is unilateral or bilateral.
Unilateral diaphragmatic paralysis (abbreviated as UDP) is often asymptomatic. In some cases, the following signs and symptoms may arise:
- Labored breathing during any physical activity (technically known as exertional dyspnea).
- Breathing difficulty in lying position (technically known as mild orthopnea).
- Reduction in endurance.
- Difficulty in breathing (dyspnea) even at rest (usually indicates presence of associated lung disease).
- Absence of breathing sounds on the affected side.
- Dull sounds upon percussion of the affected side.
- Less breathing movements on the affected side of the chest (compared to the unaffected side).
Bilateral diaphragmatic paralysis (abbreviated as BDP) is more severe than unilateral diaphragmatic paralysis, and often causes obvious signs and symptoms. The following signs and symptoms may be noted in case of bilateral diaphragmatic paralysis:
- Breathing difficulty even at rest.
- Shallow and rapid breathing.
- Breathing difficulty in lying position (severe orthopnea).
- Sleep disturbance and headaches after getting up in the morning.
- Dull or absent breathing sounds upon clinical examination.
- Signs of heart failure on right side.
- Inhalation causing inward abdominal movements.
Read more on heavy chest sensation.
Causes of Diaphragm Paralysis
The most common cause of diaphragm paralysis is nerve dysfunction. In other cases, problems with the musculature itself may cause diaphragm paralysis. In some cases, the cause may not be known. Such cases of diaphragm paralysis with unknown causes are termed idiopathic. The main causes of diaphragm paralysis can be classified as follows:
Diseases affecting the nerves
Damage to the phrenic nerve that innervates the diaphragm muscle is by far the most frequent cause of diaphragm paralysis. Phrenic nerve damage can be caused by the following conditions:
- Tumors: A variety of tumors such as mediastinal tumors, cervical spine tumors, metastatic lung cancers, and bronchial carcinomas can compress or destroy the phrenic nerve that innervates the diaphragm. Among these cancers, bronchial carcinomas are the most frequent cause of diaphragm paralysis.
- Cervical radiculopathy: Compression of the nerve root due to diseases of the cervical vertebrae can cause diaphragm paralysis.
- Shingles: Shingles is caused by a reactivation of the chicken pox virus in the body.
- Amyotrophic lateral sclerosis: Also known as the Lou-Gehrig’s disease, amyotrophic lateral sclerosis (commonly abbreviated as ALS) results in progressive destruction of nerve cells.
- Multiple sclerosis: Multiple sclerosis causes nerve dysfunction through immune-mediated destruction of the myelin sheaths that envelop nerves and aid in the conduction of nerve impulses.
- Trauma or surgery: Phrenic nerve injury may also be caused by trauma (such as accidents and birth injuries) or surgical procedures (such as thoracic surgery).
- Guillian-Barre syndrome: Guillian-Barre syndrome is characterized by an autoimmune response of the body towards the nervous system.
- Polio: Infection with polio virus frequently causes muscle weakness due to destruction of the nervous system. Diaphragmatic paralysis may occur years after a person recovers from polio (post-polio syndrome).
- Systemic lupus erythematosus: Systemic lupus erythematosus is a connective tissue disease that affects nerves along with other tissues.
Diseases affecting the muscles
A minority of cases of diaphragm paralysis are caused by conditions that affect the diaphragm muscle. However, these conditions may not be restricted to the diaphragm, and may also compromise muscle function in other parts of the body. Examples of these conditions include polymyositis, muscular dystrophy and direct injury to the diaphragm muscle.
Treatment for Paralyzed Diaphragm
Paralysis of the diaphragm is a potentially fatal condition. If the diaphragm is not functioning then breathing is severely impaired. Accessory respiratory muscles may have to take action to maintain breathing but it is not as efficient as the diaphragm.
Therefore, immediate medical attention must be sought to diagnose the cause of the problem and begin appropriate treatment. As mentioned previously, unilateral diaphragmatic paralysis may be asymptomatic. Therefore, these cases do not require treatment. Treatment for bilateral diaphragmatic paralysis include the following options:
- Positive pressure ventilatory assistance.
- Surgical flattening of the dome-shaped diaphragm to allow lung expansion (technically known as diaphragmatic plication).
- Electrical stimulation of the phrenic nerve to aid contractions of the diaphragm (technically known as diaphragmatic pacing).
- Surgical repair or grafting of the damaged phrenic nerve.